Discontinuous fiber reinforced metal matrix composite materials exhibit increased stiffness and strength in comparison to the metal which forms basis thereof, and are formable using standard metal forming equipment. Some of the more popular metal matrix composite materials are various aluminum alloys reinforced with discontinuous fibers of silicon carbide. In the process of making sheet or plate product from metal matrix composite materials, the material is typically hot rolled in several passes from a starting billet, plate or extruded plank. Generally, the rolling mills which are used to roll the metal matrix composite material are those which are also used to roll normal alloys. It has been found that during the rolling process, the resulting rolled sheet or plate of metal matrix composite material is subject to edge cracking, and that such cracking can affect from 15 to 50 percent of the rolled width. The loss of 15 percent or more of the rolled width is a severe cost penalty for the use of a material which has such desirable strength and stiffness properties. Procedures which have been attempted to reduce such edge cracking include extruding the hot pressed billets and then rolling perpendicularly to the extrusion direction. Unfortunately, such procedures have not been too successful and producers and users of metal matrix composite materials have reluctantly accepted a loss of such material due to edge cracking during the rolling process.
Because of the foregoing, it has become desirable to develop an apparatus and a method for eliminating edge cracking of metal matrix composite material during the rolling process.